PDF malware analysis — malicious · 97cfc369ac369d48

MALICIOUS

PDF

17.4 KB

MD5: 135c72406764b2b2b52d12f387972728 SHA-1: fc8cf05bef304a52e2e0bf6ba3d0a6ba346add83 SHA-256: 97cfc369ac369d48b6092f9954be44a63ad8e6edf992069dd0a8ce950d6a04bd

124 Risk Score

Malware Insights

MITRE ATT&CK

T1059.001 PowerShell

The PDF document contains embedded JavaScript, identified by multiple heuristics including PDF_JAVASCRIPT and PDF_JS. The ML classifier strongly indicates maliciousness. The JavaScript appears to be obfuscated and uses String.fromCharCode, suggesting it's designed to download and execute a second-stage payload. The extracted artifacts, javascript_obj0004_000.js, numeric_charcode_stage_000.js, and legacy_pdfkit_stage_000.js, are all JavaScript files likely involved in this process.

Machine Learning

Nyx PDF Classifier malicious score 0.9999

Heuristics 6

Annotation subject hex-decoded eval stager critical PDF_ANNOT_SUBJECT_HEX_EVAL_STAGER

PDF OpenAction JavaScript decodes a decimal char-code launcher, enumerates annotation subjects with syncAnnotScan()/getAnnots(), turns dash-delimited hex bytes into JavaScript with String.fromCharCode(), and evals the staged result. This is an exploit-kit delivery pattern and not normal PDF form logic.
JavaScript action low PDF_JAVASCRIPT

PDF contains a /JavaScript action. Generic JavaScript is common in benign forms; specific dangerous APIs are scored by separate rules.
Embedded JS stream low PDF_JS

PDF references a /JS stream. Generic JavaScript is common in benign forms; specific dangerous APIs are scored by separate rules.
String.fromCharCode low PDF_FROMCHARCODE

String.fromCharCode found — used to construct payload strings dynamically. Common in benign JavaScript libraries for codepoint manipulation, so this alone is informational; weaponised use is also caught by the dedicated fromCharCode-stage and exploit-shape rules. (matched inside decoded stream)
syncAnnotScan annotation-staging primitive low PDF_FOXIT_SYNCANNOTSCAN

PDF JavaScript calls syncAnnotScan() — a no-op annotation-enumeration primitive used by exploit-kit JavaScript to stage payload reads from annotation /Subject fields before eval(). Not a vulnerable sink itself; rarely seen in legitimate PDFs. (identified after JavaScript deobfuscation)
Suspicious extracted artifact info EXTRACTED_FILE_STATIC_TRIAGE

One or more files extracted from inside this sample matched static suspicious-content checks such as script obfuscation, encoded payload blobs, packed data, or execution/download terms.

Extracted artifacts 3

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`javascript_obj0004_000.js` `b771a67801a2a024471cb29d8ce119b13dc98b5c56ef213dece7e1a5cc7b8bed`	pdf-javascript-stream	PDF /JS object 4 at offset 0xE1	1814 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact contains 1 eval/decoder/string-building token(s).
`numeric_charcode_stage_000.js` `4718a27c2224fc36bf24f8e8e04598f1ad78adce4401c7be2708318738a6983d`	deobfuscated-js	numeric char-code string decoded JavaScript at offset 0xEF	469 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact contains 1 eval/decoder/string-building token(s).
`legacy_pdfkit_stage_000.js` `4010fb64f6e4ab16dc7918844117231c7312c28a4876957dc9e5bde136aef3e5`	deobfuscated-js	repeated-marker hex decoded JavaScript at offset 0x22FA	12073 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact contains 1 eval/decoder/string-building token(s). Carved artifact contains 1 long base64-like blob(s).

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